Resistance heating device and method for melting concrete



P. J. HYLAK Jan. 24 1967 RESISTANCE HEATING DEVICE AND METHOD FOR MELTING CONCRETE Filed Nov. 29, 1963 piz/jg /a/a I w J United States Patent 3,300,253 RESISTANCE HEATENG DEVICE AND METHOD FOR MELIING CUNQRETE Peter .I. Hylalr, Chicago, IlL, assignor to Institute of Gas Technology, a corporation of Illinois Filed Nov. 29, 1%3, Ser. No. 326,729 5 Claims. (Cl. 2914) This invention relates to a method and apparatus for melting or cutting concrete or pavement, and it particularly relates to a substantially noiseless method for breaking-up or cutting concrete or paving.

Today, in many areas and particularly in large metropolitan areas, people are subjected to a great variety of unpleasant, irritating noises, such as sirens, horns, construction noises, whistles, etc. As a result, there has been considerable effort, as in noise abatement campaigns, to eliminate or reduce the number and intensity of the sources of these noises.

One of the most prevalent and irritating of such noises results from breaking up concrete or pavement, as streets and sidewalks, by the use of air hammers. Actually, it is difficult to walk through any metropolitan area without being subjected to noises resulting from air hammers breaking up concrete or pavement. Furthermore, these air hammer noises are particularly objectionable in a normally quiet residential area and in hospital zones. Also, air hammers not only create a noise problem, but they are also quite unpleasant for the operators, who are not only subjected to the noise but are also subjected to severe vibrations.

It is therefore an important object of this invention to provide a substantially noiseless method and apparatus for breaking up or cutting concrete, pavement, streets, sidewalks, etc.

It is also an object of this invention to provide a method and apparatus for cutting concrete or pavement by melting it with a heated conductor having a melting point in excess of the concrete or pavement.

It is a further object of this invention to provide a method for breaking up concrete by melting relatively narrow portions thereof with a tungsten rod heated to a temperature of at least about 5000 F., which is well above the melting point of concrete.

It is still another object of this invention to provide a method for cutting concrete or pavement by resistance heating an electrical conductor, having a melting point in excess of the melting point of the concrete or pavement to a temperature above the-melting point of the pavement, but below the melting point of the conductor, while pushing the electrically heated conductor through the concrete or paving for effecting the cutting thereof.

Further purposes and objects of this invention will appear as the specification proceeds.

A particular embodiment of the present invention is illustrated in the accompanying drawings wherein:

FIGURE 1 is a partially sectioned, side elevational view of concrete cutting apparatus useful in the practice of my method; and

FIGURE 2 is an enlarged sectional view taken along the line of 22 of FIGURE 1.

Generally, my method for cutting or breaking up concrete or pavement comprises the steps of resistance heating an electrical conductor, having a melting point above that of the concrete or pavement, toa temperature above the melting point of concrete, but below the melting point of the conductor, and then forcing or pushing the heated conductor through the concrete or pavement in order to effect a melting or cutting of the same.

In selecting a conductor useful in my method, it is of primary importance that the conductor be constructed 3,3%,Z53 Patented Jan. 24, 1967 of a material having a melting point in excess of the melting point of the pavement or concrete; the melting point of concrete is about 2000 F. Preferably, the conductor has a melting point relatively far in excess of the melting point of the material to be cut or melted, since the higher the temperature to which the conductor is raised, the easier will be the cutting or melting operation. In selecting a suitable conductor, it is also important for the selected material to have a relatively high electrical resistance so that an excessive amount of electrical current is not required for raising the temperature of the conductor to the desired level. Although there are a number of metallic elements and alloys thereof which have the desired properties, it is preferred that the conductor be constructed of molybdenum or tungsten; preferably, tungsten is used since it has a very high melting point, being somewhat in excess of 6000 F.

When using a tungsten rod, it may be resistance heated to a temperature of about 5000 F. At this temperature the rod readily causes melting of, and cuts through the concrete or pavement, which has a much lower melting point. In the case of molybdenum, which has a melting point of about 4700 F., a rod thereof may be heated, by electrical resistance procedures to a temperature of about 4000 F., in order to effect cutting, melting, or breaking up of concrete or pavement. The temperature of the conductor is not to be raised to a point so near to its melting point as to cause softening thereof, since the conductor would then be of insufficient strength to be pushed through the material to be cut.

In order to electrically heat the conductor, electrical energy is applied to opposite ends of the preferably elongated conductor. The particular voltage and current required for raising the temperature of the rod or conductor to the desired temperature is dependent upon several factors, including the material which is used, the diameter of the rod or cross-sectional area thereof, and the particular length of the conductor. As a specific example, when using a tungsten rod, A; inch in diameter and 6 inches long, by applying a current of 200 amps and 3.0 volts to opposite ends of the rod, the temperature thereof may be raised to about 5000 F.; the electrical power requirement for this example is 600 watts. In using a tungsten rod of this diameter, no greater than 200 amps should be applied thereto, since otherwise the rod would be likely to soften and therefore lack the required structural stability to move through concrete. If the cutting rod is to be longer, the voltage is increased correspondingly; for example, if a /8 inch tungsten rod is 12 inches long, the voltage would be doubled, that is, to about 6.0 volts.

When the length is increased, it is not necessary to increase the current. However, if the diameter of the rod is increased, the current would be increased and the voltage decreased. Thus, if the inch diameter tungsten rod is doubled in diameter, the rod would require 2 or 3 times more current, but the voltage would be reduced by /2 or Generally, the power requirements for a rod having twice the diameter of another rod would be about twice as great per foot of length. In any event, it is most important that the current and voltage be sufficient to raise the temperature of the cutting instrument to a sufficiently high level to effect melting of the concrete.

After the cutting rod is at the desired temperature, it is placed against the concrete or pavement, which is to be cut or broken up, and pressure is applied to the rod to drive it through the material. In driving the cutting instrument through the material, pressure may be applied in various ways, including manual means, mechanical means, as springs or weights, etc. It has been found that by applying a normal downward force on a cutting element, for providing a pressure of 5-15 p.s.i.

since the cutting element tends to oxidize, at high temperatures, in an atmosphere of air, containing oxygen. Thus, by providing an enclosure for the cutting instrument, an inert gas may be passed into the enclosure, substantially voiding the enclosure of oxygen, thereby substantially avoiding oxidation of the cutting element. Generally, oxidation of the cutting element occurs primarily at the early stages of the cutting operation since after the cutting element penetrates the concrete, the molten concrete M in effect insulates the cutting element from the air.

Now referring to the drawings, there is shown apparatus useful in the practice of my method. The apparatus includes a generally U-shaped, continuous cutting element 12 which has an elongated base portion 14 and a pair of upstanding legs 16. As previously set forth, the cutting element 12 is preferably constructed of tungsten or molybdenum. The legs 16 and the elongated base or cutting portion 14 are formed from a single, continuous length of rod. The cross-sectional conformation of the conductor 12 may be in any desired form, including circular, rectangular, square, triangular, etc. The conductor 12 may generally be of any desired crosssectional area and length, the only requirement being that the conductor be constructed in such a manner that it may be raised to a temperature sufiicient to readily melt the concrete, without requiring unduly high voltages or currents. In this regard, a conductor 14 having a cross-section equivalent to a rod of about A; of an inch in diameter has been found to be particularly satisfactory.

The upstanding legs 16 are firmly received by the heavy copper sleeves 18, which are positioned in apertures provided in insulator support member 20. The copper connectors 18 provide electrical connections for the opposite ends of the cutting element 12, the connectors 18 being attached to the electrical leads 48 and 50. In order to provide vertical support for the base member 14 intermediate the upstanding legs 16, a plurality of upright support members or posts 22 extend between the upper surface of the base portion 14 and the lower surface of the insulator member 20. I The posts 22 are advantageously constructed of the same material as the conductor 12 so that the lower ends of the posts 22 may withstand the extremely high temperature of the conductor 12.v The distance between the conductor 12 and the insulator 20 may be varied according to the thickness of concrete'or paving through which the cutting element 12 must pass.

Desirably, an enclosure o-r hood member 24 surrounds and encloses the cutting instrument 12 in order to provide a substantially air free or oxygen free space during the cutting operation. The enclosure 24 has an open lower end, while being substantially enclosed on its other sides. An inlet 26 is provided in one side of the enclosure 24, through which an inert gas may be directed during the cutting operation in order to provide an atmosphere which will substantially prevent the oxidation of the conductor 12.

FIGURE 1 illustrates one construction which may be utilized for driving the cutting element 12 downwardly through the concrete C A pair of spring members 28 are provided and extend between the upper surface of the insulator 2t and the lower surface of the top 30 of the enclosure member 24. The springs 20 are held at their lower ends by anchoring members 32 which may be mounted within the insulator 20.

As it is desirable that the spring tension be variable so as to provide various pressures for driving the conductor 12 through the concrete, adjusting means are provided at the upper end of the springs 28. The adjusting means include threaded members or bolts 34 which threadably engage tubular members 36 which are carried in the apertures 33 provided in the top 30 of the enclosure member 24. The lower ends of the bolts 34 are rotatably secured to upper support plates 40 which abut the upper ends of the springs 28. Also, hollow sleeves or tubular members 42 provide lateral support for the springs 28, the sleeves 42 being secured to the lower surface of the top 30 0f the enclosure member 24. Thus, by rotation of the threaded member 34, the tension of the springs 28 may be adjusted to the desired degree, so that the cutting element 12 is forced through the concrete C at a desired rate of speed. Also, it is desirable that centering means he provided for moving the cutting device 12 in the same path of travel through the concrete C; preferably the cutting member 12 is maintained substantially perpendicular to the outer surface of the concrete. An upright rod member 44 is secured to the upper end of the insulator 20, and a tubular member 46 is secured to-the lower surface of the top 30 of the enclosure 24; the rod 44 is slidably received in the tubular member 46. By providing sliding movement between the rod 44 and the sleeve 46, substantially vertical movement is provided for the cutting element 12 during its path of travel through the concrete C.

The electrical leads 48 and 50 are connected to the copper connectors or sleeves 18 and provide the necessary electrical current and voltage for resistance heating the conductor 12 to the desired temperature for the melting operation.

Although, I have used the terms concrete and pavement throughout the specification, it is to be understood that these terms include within their meanings the various construction materials such as asphalt, commonly used for making streets, sidewalks, driveways, parking lots, foundations, etc.

While in the foregoing there has been provided a detailed description of a particular embodiment of the present invention, it is to be understood that all equivalents obvious to those having skill in the art are to be included within the scope of the invention as claimed.

What I claim and desire to secure by Letters Patent is:

1. A device for melting and cutting concrete comprising a U-shaped electrical conductor having an elongated base and being constructed of material having a melting point above the melting point of said concrete, means connected to the upstanding legs of said conductor for applying current and voltage to said conductor for electrically heating said conductor to a temperature above the melting point of said concrete, an insulator for supporting said upstanding legs, upright members constructed of said material and passing between the elongated base of said U-shaped conductor and said insulator in order to support said base, and means for forcing said conductor through said concrete so as to effect the melting and cutting thereof.

2. The device of claim 1 wherein said conductor and said upright members are constructed of a material selected from a group consisting of tungsten and molybdenum.

3. A device for melting and cutting concrete comprising a U-shaped tungsten rod, having upstanding legs and an elongated base, an insulator passing between and supporting the upstanding legs of said U-shaped rod, copper sleeves positioned between said insulator and said upstanding legs, electrical leads connected to said copper leads for applying voltage and current to said U- shaped rod in order to raise the temperature thereof to approximately 5000 F., upright members of tungsten passing between the elongated base of said U-shaped conductor and said insulator for supporting said conductor, an enclosure surrounding said rod for providing a substantially ogygen free space for substantially reducing oxidation of said rod, and means mounted between said enclosure and said insulator for biasing said U-shaped rod downwardly and against said concrete for forcing said rod through said concrete for the melting and cutting thereof.

4. A method for electrically melting pavement to provide an elongated cut therein, said method comprising the steps of passing an electrical current through an elongated narrow conductor of tungsten and molybdenum in order to raise the temperature of said conductor to about 5,000" F., placing said conductor against said pavement, forcing said'heated conductor through said pavement to effect the melting of said concrete to provide 1.,

the desired elongated cut, and performing said melting and cutting in a substantially oxygen free and enclosed space.

5. The method of claim 4 wherein a current of about 200 amps and a voltage of about 3.0 volts per foot of length of said conductor is applied to said conductor so as to provide the said temperature of about 5,000 E, and providing a conductor having a cross-sectional area equivalent to about inch diameter rod.

References Cited by the Examiner UNITED STATES PATENTS 640,464 1/1900 Gillett et al 175-16 X 650,124 5/1900 Coleman. 1,494,033 5/1924 Malcher 175-13 X 1,898,926 2/1933 Aarts et a1 175-16 2,308,860 l/1943 Clark 175-16 2,623,149 12/1952 Amar 175-16 2,935,593 5/1960 Fulmer 219-233 CHARLES E. OCONNELL, Primary Examiner. ERNEST R. PURSER, Examiner. 

4. A METHOD FOR ELECTRICALLY MELTING PAVEMENT TO PROVIDE AN ELONGATED CUT THEREIN, SAID METHOD COMPRISING THE STEPS OF PASSING AN ELECTRICAL CURRENT THROUGH AN ELONGATED NARROW CONDUCTOR OF TUNGSTEN AND MOLYBDENUM IN ORDER TO RAISE THE TEMPERATURE OF SAID CONDUCTOR TO ABOUT 5,000*F., PLACING SAID CONDUCTOR AGAINST SAID PAVEMENT, FORCING SAID HEATED CONDUCTOR THROUGH SAID PAVEMENT TO EFFECT THE MELTING OF SAID CONCRETE TO PROVIDE THE DESIRED ELONGATED CUT, AND PERFORMING SAID MELTING 